Antenna assembly

ABSTRACT

A dielectric substrate  101  is a square substrate having a dielectric constant εr, thickness t and length per side of Wd. A grounding conductor  102  is provided on one side of the dielectric substrate  101  in the same shape as the dielectric substrate  101.  An MSA element  103  is formed of square copper foil having a length per side of Wp in the center of the other side of the dielectric substrate  101.  Mono-pole antennas  104   a  to  104   d  are copper wires having a diameter D and length L and are spaced uniformly on diagonals of the MSA element  103  and disposed perpendicular to the dielectric substrate  101.  The MSA element  103  or mono-pole antennas  104   a  to  104   d  is selectively fed, whichever has higher reception power. When the mono-pole antennas  104   a  to  104   d  are selected, the phases and amplitudes of the respective elements are controlled. This makes it possible to obtain a high gain in all directions over a hemisphere face from the horizontal direction to the vertical direction and provide an antenna apparatus in a small and simple configuration.

TECHNICAL FIELD

The present invention relates to an antenna apparatus applicable to amicrowave band and millimeter wave band, and is suitable for use in, forexample, a fixed station apparatus in a wireless LAN system.

BACKGROUND ART

A wireless LAN system connected to a communication terminal apparatussuch as a notebook personal computer through a wireless channel isbecoming widespread in recent years. The wireless LAN system is assigneda high frequency such as a 5 GHz band and 25 GHz band. For this reason,the characteristic of a radio wave moving rectilinearly becomes morepronounced and it is increasingly difficult to secure a transmissiondistance of the radio wave. Thus, in order for one fixed stationapparatus to secure a wide area in which radio waves can be transmitted,an array antenna which forms directivities in arbitrary directions isdesigned. An invention disclosed in the Unexamined Japanese PatentPublication No. 2002-16427 is conventionally known as such an antennaapparatus.

FIG. 1A is a perspective view showing the configuration of aconventional array antenna apparatus and FIG. 1B is a cross-sectionalview showing the configuration of the conventional array antennaapparatus. In these figures, a finite reflector 11 takes the shape of acircle having a diameter on the order of 1 wavelength of an operatingfrequency and is provided with a cylindrical conductive plate 14 aroundthe perimeter thereof. A radiating element 12 has a length on the orderof ½ wavelength and is provided vertically in the center of the top faceof the finite reflector 11. A plurality of passive elements 13 arespaced uniformly around the radiating element 12, perpendicular to thetop face of the finite reflector 11. Variable reactance elements 15 areconnected to the passive elements 13 on the underside of the finitereflector 11.

In the antenna apparatus having such a configuration, it is possible toscan a principal beam in all directions within the horizontal plane bycontrolling the variable reactance elements 15 and changing thereactance value.

However, as the above described conventional technology suggests, thefixed station apparatus of the wireless LAN system may also be installedat substantially the same height as that of a communication terminalapparatus, but in this case, since there are many obstacles to radiowaves, it is desirable to install it at a relatively high place such asa ceiling for indoor use. According to the above described conventionalantenna apparatus, sufficient gains can be obtained in all directions ofthe horizontal direction, whereas sufficient gains cannot be obtained inthe vertical direction and in directions tilted from the verticaldirection. For this reason, when a conventional antenna apparatus isinstalled on, for example, the ceiling, there is a problem that it isdifficult to maintain a good communication with a communication terminalapparatus which is located at a lower position.

DISCLOSURE OF INVENTION

It is an object of the present invention to provide an antenna apparatusin a small and simple configuration capable of obtaining high gains inall directions over a hemisphere face covering from the horizontaldirection to vertical direction.

The above described object can be attained by arranging a microstripantenna element on the surface of a dielectric substrate, arranging aplurality of linear antenna elements radially on and perpendicular tothe surface of the dielectric substrate, controlling the amplitude andphase of a signal for feeding the linear antenna elements on anelement-by-element basis and selectively feeding the microstrip antennaelement or the plurality of linear antenna elements.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is a perspective view showing the configuration of aconventional array antenna apparatus;

FIG. 1B is a cross-sectional view showing the configuration of theconventional array antenna apparatus;

FIG. 2 is a perspective view showing the configuration of an antennaapparatus according to Embodiment 1 of the present invention;

FIG. 3 is a block diagram showing the configuration of the antennaapparatus according to Embodiment 1 of the present invention;

FIG. 4A illustrates a radiating pattern of the antenna apparatusaccording to Embodiment 1 of the present invention;

FIG. 4B illustrates a radiating pattern of the antenna apparatusaccording to Embodiment 1 of the present invention;

FIG. 4C illustrates a radiating pattern of the antenna apparatusaccording to Embodiment 1 of the present invention;

FIG. 5 illustrates a circular conical plane radiating pattern of amono-pole array when cut with a circular conical plane at an angle ofelevation θ of 65°;

FIG. 6 is a perspective view showing the configuration of an antennaapparatus according to Embodiment 2 of the present invention;

FIG. 7A illustrates a radiating pattern of the antenna apparatusaccording to Embodiment 2 of the present invention;

FIG. 7B illustrates a radiating pattern of the antenna apparatusaccording to Embodiment 2 of the present invention;

FIG. 7C illustrates a radiating pattern of the antenna apparatusaccording to Embodiment 2 of the present invention;

FIG. 8 illustrates a circular conical plane radiating pattern of adipole array when cut with a circular conical plane at an angle ofelevation θ of 65°;

FIG. 9 is a perspective view showing the configuration of an antennaapparatus according to Embodiment 3 of the present invention;

FIG. 10A illustrates a radiating pattern of the antenna apparatusaccording to Embodiment 3 of the present invention;

FIG. 10B illustrates a radiating pattern of the antenna apparatusaccording to Embodiment 3 of the present invention;

FIG. 10C illustrates a radiating pattern of the antenna apparatusaccording to Embodiment 3 of the present invention;

FIG. 11 illustrates a circular conical plane radiating pattern of adipole array when cut with a circular conical plane at an angle ofelevation θ of 60°;

FIG. 12 is a perspective view showing the configuration of an antennaapparatus according to Embodiment 4 of the present invention;

FIG. 13A illustrates a vertical plane radiating pattern at an azimuthangle φ=0° (X-Y plane);

FIG. 13B illustrates a vertical plane radiating pattern at an azimuthangle φ=45°;

FIG. 13C illustrates a vertical plane radiating pattern at an azimuthangle φ=90° (Y-Z plane);

FIG. 14 illustrates a circular conical plane radiating pattern of amicrostrip array when cut with a circular conical plane at an angle ofelevation θ of 25°; and

FIG. 15 illustrates a circular conical plane radiating pattern of amono-pole array when cut with a circular conical plane at an angle ofelevation θ of 70°.

BEST MODE FOR CARRYING OUT THE INVENTION

With reference now to the attached drawings, embodiments of the presentinvention will be explained below.

Embodiment 1

FIG. 2 is a perspective view showing the configuration of an antennaapparatus according to Embodiment 1 of the present invention. In thisfigure, a dielectric substrate 101 is a square substrate having adielectric constant εr, thickness t and length per side Wd.

A grounding conductor 102 has the same shape as the dielectric substrate101 and is provided on the plane in the −Z direction (see the coordinatesystem shown in FIG. 2) of the dielectric substrate 101.

A microstrip antenna element (hereinafter referred to as “MSA element”)103 is formed in the center on the plane in the +Z direction of thedielectric substrate 101 as square copper foil having a length per sideof Wp. A black bullet in the figure represents the position of a feedingpoint and is set at a position allowing impedance matching to a feeder.

Mono-pole antennas 104 a to 104 d are copper wires having a diameter D,length L, spaced uniformly (element distance d1) on the diagonals of theMSA element 103 and set perpendicular to the dielectric substrate 101.Hereinafter, the mono-pole antennas 104 a to 104 d may be collectivelycalled a “mono-pole array.”

FIG. 3 is a block diagram showing the configuration of the antennaapparatus according to Embodiment 1 of the present invention. Parts inFIG. 3 common to those in FIG. 2 are assigned the same referencenumerals as those in FIG. 2 and detailed explanations thereof will beomitted. In this figure, a mono-pole adaptive array 201 controls thephases and amplitudes of signals for feeding the mono-pole antennas 104a to 104 d and controls a maximum radiating direction and null pointdirection.

Weight adjustors 202 a to 202 d are connected to the subsequent stage ofthe mono-pole antennas 104 a to 104 d respectively and assign weights tothe phases and amplitudes of feeding signals based on the control by anadaptive processor 204.

A power distributor/combiner 203 combines power of signals input throughthe weight adjustors 202 a to 202 d, outputs the combined signal to theadaptive processor 204 and a power comparison section 206 and at thesame time outputs to a transmission/reception module 207 through ahigh-frequency switch 205. Furthermore, the power distributor/combiner203 distributes a signal output from the transmission/reception module207 to the mono-pole antennas 104 a to 104 d.

The adaptive processor 204 controls the weight adjustors 202 a to 202 dbased on signals received from the mono-pole array and signals outputfrom the power distributor/combiner 203. More specifically, the adaptiveprocessor 204 calculates the amplitudes and phases of signals receivedby the mono-pole array, measures power of signals output from the powerdistributor/combiner 203 and controls the weight adjustors 202 a to 202d so that the power (level) of the signal output from the powerdistributor/combiner 203 becomes a maximum to thereby adjust the phasesand amplitudes of the signals for feeding the mono-pole antennas 104 ato 104 d. Here, the weight adjustors 202 a to 202 d and adaptiveprocessor 204 function as control sections.

The high-frequency switch 205 as a switchover section is, for example, aPIN diode or GaAs-FET (GaAs-Field Effect Transistor), etc., and connectsan antenna which has received a signal having high power to thetransmission/reception module based on the control of the powercomparison section 206. That is, the high-frequency switch 205selectively feeds either the mono-pole antennas 104 a to 104 d or theMSA element 103.

The power comparison section 206 as a comparison section measures thepower of the signal output from the power distributor/combiner 203 andthe power of the signal received by the MSA element 103 and controls thehigh-frequency switch 205 for operating the antenna which has received asignal with high power based on the result of a comparison to decidewhich power is higher.

The transmission/reception module 207 carries out predeterminedreception processing such as A/D conversion and down-conversion andpredetermined transmission processing such as D/A conversion andup-conversion.

Next, the operation of the antenna apparatus having the above describedconfiguration will be explained. The power comparison section 206compares the combined power of signals received by the mono-pole arrayand the power of the signal received by the MSA element 103 and controlsthe high-frequency switch 205 so as to connect the antenna with higherpower to the transmission/reception module. Here, suppose the mono-polearray is selected as the operating antenna.

The adaptive processor 204 calculates the amplitudes and phases of thesignals received by the mono-pole antennas 104 a to 104 d. The adaptiveprocessor 204 also measures the combined power of the weight-adjustedreceived signal. In order to adjust the phases and amplitudes of signalsreceived by the respective mono-pole antennas 104 a to 104 d so that thecombined power becomes a maximum, the adaptive processor 204 controlsthe weight adjustors 202 a to 202 d. This makes it possible to changedirectivity on the horizontal plane (X-Y plane shown in FIG. 2) anddirect the maximum radiating direction in an arbitrary direction.

When the power comparison section 206 selects the MSA element 103 as theoperating antenna, the high-frequency switch 205 connects the MSAelement 103 and transmission/reception module 207.

Thus, by selectively feeding the mono-pole array and MSA element 103based on the reception power, it is possible to radiate stable radiowaves. At the time of transmission, the antenna used for reception canbe selected.

Next, the radiation characteristic when the operating frequency of theabove described antenna apparatus is set as 5.2 GHz will be explainedmore specifically.

Here, parameters for configuring the antenna apparatus shown in FIG. 2will be set as follows:

-   εr=2.6-   t=1.5 [mm]-   Wd=80 [mm] (approximately 1.4 wavelength)-   Wp=15.5 [mm]-   D=1 [mm]-   L=29 [mm] (approximately 0.5 wavelength)-   d1=29 [mm] (approximately 0.5 wavelength)

FIG. 4A to C illustrate radiating patterns of the antenna apparatusaccording to Embodiment 1 of the present invention. In FIG. 4A to C,solid lines represent radiating patterns of the MSA element 103 anddotted lines represent radiating patterns of the mono-pole array.

FIG. 4A is a vertical plane radiating pattern at an azimuth angle φ=0°(X-Z plane) with respect to the coordinate axis in FIG. 2. For theradiating pattern of the mono-pole array at this time, the phases of themono-pole antennas 104 a and 104 c are set to 0° and the phases of themono-pole antennas 104 b and 104 d are set to 180° so that the azimuthangle φ in the maximum radiating direction becomes 0°.

FIG. 4B is a vertical plane radiating pattern at an azimuth angle φ=45°.For the radiating pattern of the mono-pole array at this time, the phaseof the mono-pole antenna 104 a is set to 0°, the phases of the mono-poleantennas 104 b and 104 c are set to −127.3° and the phase of themono-pole antenna 104 d is set to 105.4° so that the azimuth angle φ inthe maximum radiating direction becomes 45°.

FIG. 4C is a vertical plane radiating pattern at an azimuth angle φ=90°(Y-Z plane). For the radiating pattern of the mono-pole array at thistime, the phases of the mono-pole antennas 104 a and 104 b are set to 0°and the phases of the mono-pole antennas 104 c and 104 d are set to 180°so that the azimuth angle φ in the maximum radiating direction becomes90°.

As is evident from FIG. 4A to C, the maximum radiating direction of theMSA element 103 is a +Z direction and the maximum gain is 9.4 [dBi].Furthermore, the angle of elevation θ in the maximum radiating directionof the mono-pole array is approximately 65° and the maximum gain isapproximately 8 [dBi]. Furthermore, in the direction in which the angleof elevation θ is approximately 45°, both the gain of the MSA element103 and the gain of the mono-pole array drop and become equal, but gainsof 4 [dBi] or above are obtained.

When the azimuth angle φ in the maximum radiating direction of themono-pole array is changed by adjusting the phases of the mono-poleantennas 104 a to 104 d, the vertical plane radiating pattern at φ=180°has a characteristic substantially equivalent to that in FIG. 4A and thevertical plane radiating patterns at φ=135°, 225°, 315° havecharacteristics substantially equivalent to that in FIG. 4B and thevertical plane radiating pattern at φ=270° has a characteristicsubstantially equivalent to that in FIG. 4C.

FIG. 5 illustrates a circular conical plane radiating pattern of amono-pole array when cut with a circular conical plane at an angle ofelevation θ of 65°. In this figure, solid lines 401 represent a circularconical plane radiating pattern of the mono-pole array in FIG. 4A,dotted lines 402 represent a circular conical plane radiating pattern ofthe mono-pole array in FIG. 4B and single-dot dashed lines 403 representa circular conical plane radiating pattern of the mono-pole array inFIG. 4C.

As is evident from this figure, by changing the phases of the mono-poleantennas 104 a to 104 d, it is possible to direct the maximum radiatingdirection of the mono-pole array to all directions of the horizontalplane.

Having such a radiation characteristic, when the antenna apparatushaving the above described configuration is attached to, for example, anindoor ceiling, the +Z direction corresponds to the floor direction andthe −Z direction corresponds to the ceiling side. That is, when thedirectivity is preferred to be directed to the floor direction (highangle of elevation with an angle of elevation θ of 45° or less), the MSAelement 103 is selected as the operating antenna. On the other hand,when the directivity is preferred to be directed to a low angle ofelevation direction with an angle of elevation θ of 45° or above, themono-pole array is selected as the operating antenna. Thus, by selectingand operating either the MSA element 103 or the mono-pole array, it ispossible to obtain a sufficient gain of 4 [dBi] or above in alldirections over the hemisphere face in the +Z direction. That is, theabove described antenna apparatus is suitable for use in a fixed stationapparatus installed in a higher place than a communication terminalapparatus.

Thus, according to this embodiment, a microstrip antenna is placed onthe surface of a dielectric substrate, four mono-pole antennas arespaced uniformly around the microstrip antenna and perpendicular to thedielectric substrate plane to thereby form a mono-pole array, and themicrostrip antenna and mono-pole array are selectively fed to realize anantenna apparatus which can obtain a high gain in all directions overthe hemisphere face in the +Z direction. Furthermore, it is alsopossible to realize an antenna apparatus in a small and simpleconfiguration.

Embodiment 2

FIG. 6 is a perspective view showing the configuration of an antennaapparatus according to Embodiment 2 of the present invention. In thisfigure, a dielectric substrate 503 is a square substrate having adielectric constant εr, thickness t and length per side of Wd and asquare hollow section (hole) 502 having a length per side of Wh isformed in the center of the substrate.

A grounding conductor 503 has the same shape as the dielectric substrate501 and is provided on the plane in the −Z direction of the dielectricsubstrate 501.

An MSA element 504 is formed of square copper foil having a length perside of Wp and the center of the copper foil is punched out in the sameshape as the hollow section 502. The MSA element 504 is placed on thesurface of the dielectric substrate 501 in the +Z direction in thepunched out section aligned with the hollow section 502. A black bulletin the figure represents the position of a feeding point and is set at aposition allowing impedance matching to a feeder.

The base of a column 505 is fixed by the hollow section 502 andsupporting members 506 a to 506 d are radially spliced together at aheight of approximately L/2 from the base.

The supporting members 506 a to 506 d are provided parallel to thediagonals of the MSA element 504, tips of the supporting members 506 ato 506 d are located at the vertices of a square having a length perside of d1 and the dipole antenna 507 a to 507 d are supported by thetips of the supporting members 506 a to 506 d at their center. Thismakes it possible to even support antenna elements such as dipoleantennas which cannot be directly placed on the dielectric substrate501.

The dipole antennas 507 a to 507 d are copper wires having a diameter Dand length L and arranged at a distance of h from the dielectricsubstrate 501 and perpendicular to the dielectric substrate 501.

Feeder paths 508 a to 508 d are provided inside the column 505 andsupporting members 506 a to 506 d to feed the dipole antennas 507 a to507 d at the tips of the supporting members 506 a to 506 d.

The column 505 and supporting members 506 a to 506 d, even when made ofmetal, have little influence on the operation of the antenna apparatus,but they are preferably made of resin so as not to have the leastinfluence on the operation of the antenna apparatus.

In this embodiment as well as Embodiment 1, the operating antenna isalso selected based on a comparison between the power of a signalreceived by the MSA element 504 and the power of signals received by thedipole array.

Next, the radiation characteristic when the operating frequency of theabove described antenna apparatus is set to 5.2 GHz will be explainedmore specifically.

Here, parameters configuring the antenna apparatus shown in FIG. 6 willbe set as follows.

-   εr=2.6-   t=1.5 [mm]-   Wd=80 [mm] (approximately 1.4 wavelength)-   Wp=15.5 [mm]-   D=1 [mm]-   L=29 [mm] (approximately 0.5 wavelength)-   d1=29 [mm] (approximately 0.5 wavelength)-   h=1 [mm]-   Wh=8 [mm]

FIG. 7A to C illustrate radiating patterns of the antenna apparatusaccording to Embodiment 2 of the present invention. In FIG. 7A to C,solid lines represent radiating patterns of the MSA element 504 anddotted lines represent radiating patterns of the dipole array.

FIG. 7A is a vertical plane radiating pattern at an azimuth angle φ=0°(X-Z plane) with respect to the coordinate axis in FIG. 6. For theradiating pattern of the dipole array at this time, the phases of thedipole antennas 507 a and 507 c are set to 0° and the phases of thedipole antennas 507 b and 507 d are set to 180° so that the azimuthangle φ in the maximum radiating direction becomes 0°.

FIG. 7B is a vertical plane radiating pattern at an azimuth angle φ=45°.For the radiating pattern of the dipole array at this time, the phase ofthe dipole antenna 507 a is set to 0° and the phases of the dipoleantennas 507 b and 507 c are set to −127.3° and the phase of the dipoleantenna 507 d is set to 105.4° so that the azimuth angle θ in themaximum radiating direction of the dipole array becomes 45°.

FIG. 7C is a vertical plane radiating pattern at an azimuth angle φ=90°(Y-Z plane). For the radiating pattern of the dipole array at this time,the phases of the dipole antennas 507 a and 507 b are set to 0° and thephases of the dipole antennas 507 c and 507 d are set to 180° so thatthe azimuth angle φ in the maximum radiating direction of the dipolearray becomes 90°.

As is evident from FIG. 7A to C, the maximum radiating direction of theMSA element 504 is the +Z direction and the maximum gain is 8.1 [dBi].Furthermore, the angle of elevation θ in the maximum radiating directionof the dipole array is approximately 65° and the maximum gain isapproximately 7.5 [dBi]. Furthermore, in the direction with the angle ofelevation θ of approximately 45°, both the gain of the MSA element 504and the gain of the dipole array drop and become equal, but gains of 4[dBi] or above are obtained.

When the azimuth angle φ in the maximum radiating direction of thedipole array is changed by adjusting the phases of the dipole antennas507 a to 507 d, the vertical plane radiating pattern at φ=180° has acharacteristic substantially equivalent to that in FIG. 7A and thevertical plane radiating patterns at φ=135°, 225°, 315° havecharacteristics substantially equivalent to that in FIG. 7B and thevertical plane radiating pattern at φ=270° has a characteristicsubstantially equivalent to that in FIG. 7C.

FIG. 8 illustrates a circular conical plane radiating pattern of adipole array when cut with a circular conical plane at an angle ofelevation θ of 65°. In this figure, solid lines 701 represent a circularconical plane radiating pattern of the dipole array in FIG. 7A, dottedlines 702 represent a circular conical plane radiating pattern of thedipole array in FIG. 7B and single-dot dashed line 703 represent acircular conical plane radiating pattern of the dipole array in FIG. 7C.

As is evident from this figure, by changing the phases of the dipoleantennas 507 a to 507 d, it is possible to direct the maximum radiatingdirection of the dipole array to all directions of the horizontal plane.

Having such a radiation characteristic, when the directivity ispreferred to be directed to a direction with a high angle of elevation θof 45°0 or less, the MSA element 504 is selected as the operatingantenna and when the directivity is preferred to be directed to adirection with a low angle of elevation θ of 45° or above, the dipolearray is selected as the operating antenna. Thus, by selecting andoperating either the MSA element 504 or the dipole array, it is possibleto obtain a sufficient gain of 4 [dBi] or above in all directions overthe hemisphere face in the +Z direction.

Thus, according to this embodiment, a microstrip antenna is placed onthe surface of a dielectric substrate, four dipole antennas are spaceduniformly around the microstrip antenna and perpendicular to the surfaceof the dielectric substrate to thereby form a dipole array, and themicrostrip antenna and dipole array are selectively fed to realize anantenna apparatus which can obtain a high gain in all directions overthe hemisphere face in the +Z direction.

In this embodiment, a column is provided in the center of the dielectricsubstrate, supporting members are spliced with the column and dipoleantennas are supported by the tips of the supporting members, but it isalso possible to provide a plurality of columns around the dielectricsubstrate, splice the supporting members with the respective columns sothat the supporting members support the dipole antennas

Embodiment 3

FIG. 9 is a perspective view showing the configuration of an antennaapparatus according to Embodiment 3 of the present invention. However,parts in FIG. 9 common to those in FIG. 6 are assigned the samereference numerals as those in FIG. 6 and detailed explanations thereofwill be omitted. What FIG. 9 mainly differs from FIG. 6 is that thedipole array has a two-stage structure.

The base of a column 801 is fixed by a hollow section 502, supportingmembers 506 a to 506 d and supporting members 802 a to 802 d areradially spliced at heights on the order of L/2 and 3L/2 from the baserespectively.

The supporting members 802 a to 802 d are placed at a distance d2 fromthe supporting members 506 a to 506 d in parallel thereto and the tipsof the supporting members are located at vertices of a square having alength per side of d1 and the tips of the supporting members 802 a to802 d support the dipole antennas 803 a to 803 d at their respectivecenters.

The dipole antennas 803 a to 803 d are made of copper wires havingdiameter D and length L and arranged on the extensions of dipoleantennas 507 a to 507 d. That is, this antenna apparatus has a two-stagestructure of dipole arrays each consisting of 4 elements. In this way,it is possible to control directivities adaptively on the vertical planeas well as the horizontal plane by adjusting the phase of each dipoleantenna.

Hereinafter, the dipole antennas 507 a to 507 d closer to the dielectricsubstrate surface may be referred to as a first dipole array and thedipole antennas 803 a to 803 d farther from the dielectric substratesurface may be referred to as a second dipole array.

The feeder paths 804 a to 804 d are laid inside the column 801 andsupporting members 802 a to 802 d and feed the dipole antennas 803 a to803 d at the tips of the supporting members 802 a to 802 d.

In this embodiment as well as Embodiment 1, an operating antenna isselected based on a comparison between the power of a signal received byan MSA element 504 and the power of the signal received by the first andsecond dipole arrays.

Next, the radiation characteristic when the operating frequency of theantenna apparatus is set to 5.2 GHz will be explained more specifically.

Here, parameters constituting the antenna apparatus shown in FIG. 9 areset as follows.

-   εr=2.6-   t=1.5 [mm]-   Wd=80 [mm] (approximately 1.4 wavelength)-   Wp=15.5 [mm]-   D=1 [mm)-   L=29 [mm] (approximately 0.5 wavelength)-   d1=29 [mm] (approximately 0.5 wavelength)-   d2=30 [mm] (approximately 0.5 wavelength)-   h=1 [mm]-   Wh=8 [mm]

FIG. 10 illustrates radiating patterns of the antenna apparatusaccording to Embodiment 3 of the present invention. In FIG. 10A to C,solid lines represent a radiating pattern of the MSA element 504, dottedlines represent a radiating pattern when the phase of the first dipolearray is 45° ahead of the phase of the second dipole array andsingle-dot dashed lines represent a radiating pattern when the phase ofthe first dipole array is 120° ahead of the phase of the second dipolearray.

In FIG. 10A, the phase of the dipole array is adjusted so that themaximum radiating direction of the dipole array is directed to thedirection with the azimuth angle φ of 0° on the coordinate axis in FIG.9. Furthermore, the phase of the dipole array is adjusted so that themaximum radiating direction of the dipole array is directed to thedirection with the azimuth angle φ of 45° in FIG. 10B and the directionwith the azimuth angle φ of 90° in FIG. 10C respectively.

As is clear from FIG. 10A to C, the maximum radiating direction of theMSA element 504 is in the +Z direction and the maximum gain is 6.3[dBi]. Furthermore, an angle of elevation θ in the maximum radiatingdirection of the dipole array can be changed within a range of 60° to75° by providing a phase difference between the first dipole array andsecond dipole array and the maximum gain is 9 [dBi] or above.

Furthermore, in the direction with the angle of elevation θ ofapproximately 35°, both the gain when the phase of the first dipolearray is 120° ahead of the phase of the second dipole array (single-dotdashed line shown in FIG. 10) and gain of the MSA element 504 drop andbecome the same, but a gain of approximately 4 [dBi] or above can beobtained.

When the azimuth angle φ in the maximum radiating direction of thedipole array is changed by adjusting the phases of the dipole antennas507 a to 507 d and 803 a to 803 d, the vertical plane radiating patternat φ=180° has a characteristic substantially equivalent to that in FIG.10A, the vertical plane radiating patterns at φ=135°, 225°, 315° havecharacteristics substantially equivalent to those in FIG. 10B and thevertical plane radiating pattern at φ=270° has a characteristicsubstantially equivalent to that in FIG. 10C.

FIG. 11 illustrates a circular conical plane radiating pattern of thedipole array when cut with a circular conical plane at an angle ofelevation θ of 60°. This figure shows a radiating pattern of the dipolearray when the phase of the first dipole array is 120° ahead of thephase of the second dipole array. Solid lines 1001 represent a circularconical plane radiating pattern of the dipole array in FIG. 10A, dottedlines 1002 represent a circular conical plane radiating pattern of thedipole array in FIG. 10B and single-dot dashed lines 1003 represent acircular conical plane radiating pattern of the dipole array in FIG.10C.

As is evident from this figure, adopting a two-stage structure of dipolearrays makes it possible to control directivity on a vertical plane at alow angle of elevation and increase the gain in a low angle of elevationdirection.

Thus, this embodiment constructs a two-stage structure of dipole arraysfrom eight dipole antennas each stage consisting of four dipole antennasand selectively feeds the microstrip antenna and dipole arrays, and canthereby realize directivity control on the vertical plane at a low angleof elevation in addition to the effect of Embodiment 2 and increase thegain in a low angle of elevation direction.

Embodiment 4

FIG. 12 is a perspective view showing the configuration of an antennaapparatus according to Embodiment 4 of the present invention. However,parts in FIG. 12 common to FIG. 2 are assigned the same referencenumerals as those in FIG. 2 and detailed explanations thereof will beomitted.

MSA elements 103 a to 103 d are formed of square copper foil having alength per side of Wp on the surface of a dielectric substrate 101 inthe +Z direction. The MSA elements 103 a to 103 d are spaced uniformlyin the X direction and Y direction. At this time, the element distanceof the MSA elements 103 a to 103 d is set to d3. The phases andamplitudes of signals of the MSA elements 103 a to 103 d are adjusted byan adaptive processor and weight adjustor (not shown) and directivitiescontrolled. The MSA elements 103 a to 103 d hereinafter may also bereferred to as a “microstrip array.”

The mono-pole antennas 104 a to 104 d are copper wires having a diameterD and length L and spaced uniformly (element distance d1) between theMSA elements and placed perpendicular to the dielectric substrate 101.

In this embodiment as well as Embodiment 1, an operating antenna isselected based on a comparison between the power of a signal received bya microstrip array and the power of a signal received by a mono-polearray.

Next, the radiation characteristic when the operating frequency of theantenna apparatus is set to 5.2 GHz will be explained more specifically.

Here, parameters constituting the antenna apparatus shown in FIG. 12will be set as follows.

-   εr=2.6-   t=1.5 [mm]-   Wd=80 [mm] (approximately 1.4 wavelength)-   Wp=15.5 [mm]-   D=1 [mm]-   L=29 [mm] (approximately 0.5 wavelength)-   d1=29 [mm] (approximately 0.5 wavelength)-   d3=29 [mm] (approximately 0.5 wavelength)

FIG. 13A to C illustrate radiating patterns of the antenna apparatusaccording to Embodiment 4. In FIG. 13A to C, solid lines represent aradiating pattern of the microstrip array when the MSA elements 103 a to103 d are have the same phase, dotted lines represent a radiatingpattern of the microstrip array when the phases of the MSA elements 103a to 103 d are changed and single-dot dashed lines represent a radiatingpattern of the mono-pole array.

FIG. 13A is a vertical plane radiating pattern at an azimuth angle φ=0°(X-Z plane) with respect to the coordinate axis in FIG. 12. Theradiating pattern represented by dotted lines at this time shows thecase where the phases of the MSA elements 103 a and 103 c are the sameand 120° behind the phases of the MSA elements 103 b and 103 d.Furthermore, the radiating pattern of the mono-pole array represented bya single-dot dashed line shows the case where the phases of themono-pole antennas 104 a and 104 d are set to 0°, the phase of themono-pole antenna 104 b is set to −127.3° and the phase of the mono-poleantenna 104 c is set to 127.3°.

FIG. 13B shows a vertical plane radiating pattern at an azimuth angleφ=45°. The radiating pattern represented by a dotted line at this timeshows the case where the phase of the MSA element 103 a is set to 0°,the phases of the MSA elements 103 b and 103 c are set to −120° and thephase of the MSA element 103 d is set to −240°. Furthermore, theradiating pattern of the mono-pole array represented by single-dotdashed lines shows the case where the phases of mono-pole antennas 104 aand 104 c are set to 0° and the phases of the mono-pole antennas 104 band 104 d are set to 180°.

FIG. 13C shows a vertical plane radiating pattern at an azimuth angleφ=90° (Y-Z plane). The radiating pattern represented by a dotted line atthis time shows the case where the phases of the MSA elements 103 a and103 b are the same and 120° behind the phases of the MSA elements 103 cand 103 d. Furthermore, the radiating pattern of the mono-pole arrayrepresented by a single-dot dashed line shows the case where the phaseof the mono-pole antenna 104 a is set to 127°, the phases of themono-pole antennas 104 b and 104 c are set to 0° and the phase of themono-pole antenna 104 d is set to −127.3°.

As is clear from FIG. 13, the angle of elevation θ of the maximumradiating direction of the microstrip array can be changed within arange of 0° to 25° by providing a phase difference between the MSAelements 103 a to 103 d and the maximum gain is 10 [dBi] or above.Furthermore, the angle of elevation θ in the maximum radiating directionof the mono-pole array is approximately 70° and the maximum gain is 7[dBi] or above.

Furthermore, in the direction with the angle of elevation θ ofapproximately 55°, both the gain of the microstrip array and the gain ofthe mono-pole array drop and become the same, but gains of approximately7 [dBi] or above can be obtained.

FIG. 14 illustrates a circular conical plane radiating pattern of themicrostrip array when cut with a circular conical plane at an angle ofelevation θ of 25°. In this figure, a solid line 1301 represents acircular conical plane radiating pattern of the microstrip arrayrepresented by the dotted line in FIG. 13A, a dotted line 1302represents a circular conical plane radiating pattern of the microstriparray represented by the dotted line in FIG. 13B and a single-dot dashedline 1303 represents the circular conical plane radiating pattern of themicrostrip array in FIG. 13C.

As is clear from this figure, it is possible to direct the maximumradiating direction of the microstrip array to all directions within thehorizontal plane at a high angle of elevation θ of 25° by changing thephases of the MSA elements 103 a to 103 d.

Furthermore, FIG. 15 illustrates a circular conical plane radiatingpattern of the mono-pole array in FIG. 13 when cut with a circularconical plane at an angle of elevation θ of 70°. In this figure, a solidline 1401 represents the circular conical plane radiating pattern of themono-pole array in FIG. 13A, a dotted line 1402 represents the circularconical plane radiating pattern of the mono-pole array in FIG. 13B and asingle-dot dashed line 1403 represents the circular conical planeradiating pattern of the mono-pole array in FIG. 13C.

As is clear from this figure, it is possible to direct the maximumradiating direction of the mono-pole array to all directions within thehorizontal plane by changing the phases of the mono-pole antennas 104 ato 104 d.

Having such a radiation characteristic, the MSA elements 103 a to 103 dare selected as the operating antennas when directivity is controlled ina high angle of elevation direction at an angle of elevation θ of 45° orless and the mono-pole antennas 104 a to 104 d are selected as theoperating antennas when directivity is controlled in a low angle ofelevation direction at an angle of elevation θ of 45° or above. Thus, itis possible to obtain a sufficient gain of 7 [dBi] or above in alldirections over the hemisphere face in the +Z direction by selecting andoperating either the microstrip array or mono-pole array.

Thus, this embodiment arranges a microstrip array made up of 4 elementsand a mono-pole array made up of 4 elements on a dielectric substratesurface, selectively feeds the respective array antennas and controlsthe phases of the respective elements to be fed, and can thereby obtaina higher gain in all directions over a hemisphere face in the +Zdirection and control directivity not only at a low angle of elevationbut also at a high angle of elevation.

The above described embodiments have been explained assuming that thenumber of linear antenna elements is four (the number of antennaelements in each stage in the case of Embodiment 3), but the presentinvention is not limited to this and the number of linear antennaelements can be plural, not smaller than 3.

Furthermore, the above described embodiments have been explainedassuming that the dielectric substrate and MSA element have a squareshape, but the present invention is not limited to this. The linearantenna elements need not always be spaced uniformly on diagonals of theMSA element, either but can be arranged radially.

Furthermore, the parameters making up the antenna apparatus shown in theabove described embodiments can be any parameters if they at least allowa predetermined radiation characteristic to be obtained according to theoperating frequency band.

Furthermore, the above described embodiments can be implemented bymodifying and combining the parameters making up the antenna apparatusas appropriate.

Furthermore, the above described embodiments selectively feed the linearantenna array and MSA elements (microstrip array) based on the power ofsignals received by the respective antennas, but the present inventioncan also be adapted so as to selectively feed them based on S/N ratiosof the respective antennas and parameters indicating the reception statesuch as field intensity.

The antenna apparatus of the present invention adopts a configurationcomprising a dielectric substrate having a predetermined dielectricconstant, a microstrip antenna element placed on the surface of thedielectric substrate, a plurality of linear antenna elements arrangedradially on and perpendicular to the surface of the dielectricsubstrate, a control section that controls the amplitudes and phases ofsignals for feeding the linear antenna elements on an element-by-elementbasis and a switchover section that selectively feeds the microstripantenna element or the plurality of linear antenna elements.

According to this configuration, the plurality of linear antennaelements arranged perpendicular to the surface of the dielectricsubstrate are fed by signals whose amplitudes and phases are controlled,and it is thereby possible to direct a maximum radiating direction to anarbitrary direction horizontal to the surface of the dielectricsubstrate and the provision of the microstrip antenna element allows theradiating direction to be directed to the direction perpendicular to thesurface of the dielectric substrate.

In the antenna apparatus of the present invention having the abovedescribed configuration, the switchover section comprises a comparisonsection that compares the reception state of the plurality of linearantenna elements and the reception state of the microstrip antennaelement and the antenna element which has received a signal whosereception state is decided to be good by the comparison section is fed.

According to this configuration, of the microstrip antenna element andthe plurality of linear antenna elements which have received signals, anantenna whose reception state is good is fed, and it is thereby possibleto realize stable emission of radio waves.

The antenna apparatus according to the present invention in the abovedescribed configuration adopts a configuration comprising a holeprovided in the center of the microstrip antenna element penetrating themicrostrip antenna element and the dielectric substrate, a columnprovided in the hole and supporting members radially spliced from thecolumn that support the linear antenna elements.

According to this configuration, it is possible to even support antennaelements such as dipole antennas which cannot be directly placed on thedielectric substrate.

In the antenna apparatus according to the present invention in the abovedescribed configuration, the plurality of linear antenna elements arearranged in multiple stages in the direction perpendicular to thesurface of the dielectric substrate.

According to this configuration, by arranging the plurality of linearantenna elements in multiple stages and thereby providing a phasedifference between the stages, it is possible to realize directivitycontrol on the vertical plane at a low angle of elevation and increasethe gain at in a low angle of elevation direction.

In the antenna apparatus according to the present invention in the abovedescribed configuration, a plurality of the microstrip antenna elementsare arranged on the dielectric substrate and the control sectioncontrols the amplitudes and phases of signals for feeding the pluralityof microstrip antenna elements on an element-by-element basis.

According to this configuration, it is possible to obtain a higher gainand control directivities at a high angle of elevation by feeding theplurality of linear antenna elements arranged on the surface of thedielectric substrate using signals whose amplitudes and phases arecontrolled.

The antenna apparatus according to the present invention in the abovedescribed configuration, mono-pole antennas or dipole antennas can beused as the plurality of linear antenna elements.

According to this configuration, whether mono-pole antennas or dipoleantennas are used as the linear antenna elements, similar radiatingpatterns are obtained, and therefore it is possible to use any desiredantennas.

As described above, the present invention arranges a microstrip antennaelement on the surface of a dielectric substrate, arranges a pluralityof linear antenna elements radially on and perpendicular to the surfaceof the dielectric substrate, controls the amplitudes and phases ofsignals for feeding the linear antenna elements on an element-by-elementbasis and selectively feeds the microstrip antenna element or theplurality of linear antenna elements, and can thereby realize an antennaapparatus capable of obtaining a high gain in all directions over athree-dimensional area on the surface of the dielectric substrate.Furthermore, the present invention can also realize an antenna apparatusin a small and simple configuration.

This application is based on the Japanese Patent Application No.2003-041492 filed on Feb. 19, 2003, entire content of which is expresslyincorporated by reference herein.

INDUSTRIAL APPLICABILITY

The present invention relates to an antenna apparatus applicable to amicrowave band and millimeter wave band and is suitable for use in, forexample, a fixed station apparatus in a wireless LAN system.

1. An antenna apparatus comprising: a dielectric substrate having apredetermined dielectric constant; a microstrip antenna element placedon the surface of said dielectric substrate; a plurality of linearantenna elements arranged radially on and perpendicular to the surfaceof said dielectric substrate; a control section that controls theamplitudes and phases of signals for feeding said linear antennaelements on an element-by-element basis; and a switchover section thatselectively feeds said microstrip antenna element or said plurality oflinear antenna elements.
 2. The antenna apparatus according to claim 1,wherein said switchover section comprises a comparison section thatcompares the reception state of said plurality of linear antennaelements and the reception state of said microstrip antenna element, andthe antenna element which has received a signal whose reception state isdecided to be good by said comparison section is fed.
 3. The antennaapparatus according to claim 1, further comprising: a hole provided inthe center of said microstrip antenna element penetrating saidmicrostrip antenna element and said dielectric substrate; a columnprovided in said hole; and supporting members radially spliced from saidcolumn that support said linear antenna elements.
 4. The antennaapparatus according to claim 1, wherein said plurality of linear antennaelements are arranged in multiple stages in the direction perpendicularto the surface of said dielectric substrate.
 5. The antenna apparatusaccording to claim 4, wherein said control section controls the phasesof signals for feeding said plurality of multi-staged linear antennaelements on an element-by-element basis.
 6. The antenna apparatusaccording to claim 1, wherein a plurality of said microstrip antennaelements are arranged on said dielectric substrate and said controlsection controls the amplitudes and phases of signals for feeding saidplurality of microstrip antenna elements on an element-by-element basis.7. The antenna apparatus according to claim 1, wherein mono-poleantennas or dipole antennas are used as said plurality of linear antennaelements.